Halogen lamp employing a quartz envelope provided with a colored layer

ABSTRACT

A colored halogen lamp having a quartz envelope that has been coated with a layer of luster lacquer, essentially consisting of metal salts of resin acids dissolved in ethereal oils. The coating is fired up to temperatures between 500* C. and 600* C.

United States Patent Inventors l-lenricus Antonius Van Bakel;

Riksterus Aguste Jahannes Marla Melier, both of Emmasingel, Eindhoven, Netherlands Appl. No. 781,966

Filed Dec. 6, 1968 Patented Nov. 2, 1971 Assignee U. S. Philips Corporation New York, N.Y.

Priority Dec. 15, 1967 Netherlands 6717090 HALOGEN LAMP EMPLOYING A QLJARTZ ENVELOPE PROVIDED WITH A COLORED LAYER Field of Search [56] References Cited UNITED STATES PATENTS 3,066,040 1 H1962 Swanson 1 17/94 3,094,642 6/1963 Duval 313/223 3,237,043 2/1966 Schrodem. 313/223 3,263,113 7/1966 Schroder... 313/223 3,420,694 1/1969 James 117/94 Primary Examiner-Alfred L. Leavitt Assistant Examiner-Edward G. Whitby Attorney-Frank R. Trifari ABSTRACT: A colored halogen lamp having a quartz envelope that has been coated with a layer of luster lacquer, essentially consisting of metal salts of resin acids dissolved in ethereal oils. The coating is fired up to temperatures between 500C. and 600C. V

HALOGEN LAMP EMPLOYING A QUARTZ ENVELOPE PROVIDED WITH A COLORED LAYER The invention relates to a halogen lamp employing a quartz envelope provided with acolored layer. Quartz is to be understood in this connection to include a glass having a content of silica of more than 96 percent which is obtained from a borosilicate glass from which, after phase separation, the boric acid has been removed substantially by leaching and is then sintered. A halogen lamp is to be understood to mean herein a lamp having a quartz envelope with a comparatively small capacity, the tungsten filament in the envelope being surrounded by an atmosphere which, in addition to a rare gas and/or nitrogen, contains a reactive transport gas, for example, iodine, bromine together with hydrogen, or chlorine together with hydrogen, as such or in the form of a compound, the temperature of the wall of the envelope during operation increasing to a value at which tungsten-halogen compounds formed in the lamp can not condense. As a result of this the wall of the envelope of the halogen lamp remains bright until the end of the life, which life ends at the instant the filament fuses.

In practice, the temperature of the wall of the envelope during operation of the lamp lies between approximately 500 C.

and 600 C.

For certain purposes and in given circumstances, there exists a need of colored light, for example, yellow light for automohile headlights, blue for photographic purposes, red for infrared applications, orange for use in flashing lights and traffic lights.

The desired colored light can be obtained by using light filters. However, this meets with difficulties when used in combination with halogen lamps, which drawbacks are associated with the large quantity of energy which is irradiated by these lamps in the form of light and heat.

The commonly used color methods for conventional filament lamps with glass envelopes in which a dye or a pigmentation agent, whether or not in a binder, is used cannot be applied with halogen lamps because quartz has a very low coefficient of thermal expansion as compared with the coefficient of expansion of the colored layers provided according to the methods and because of the high-energy load of the wall of the envelope oxidation may occur associated with a change in color of the colored layers provided in accordance with these known methods. Moreover, those methods, with which a colored layer is provided on the inner Wall of the envelope cannot be used either in connection with the presence of the reactive transport gas.

lt is the object of the invention to overcome these difficulties.

According to the invention, the envelope of a halogen lamp consists of quartz provided with a fired colored luster lacquer layer.

Such a layer is obtained by providing on the quartz envelope of a halogen lamp a layer of a luster lacquer and then firing it, preferably at a temperature which lies above the temperature which the wall of the envelope reaches during operation.

Luster lacquers are solutions of metal salts of resin acids in ethereal oils. Upon baking, metal oxide skins in a thickness in the order of mm. are formed. They are used for decorating and adorning articles of porcelain, glass, and ceramic material. It has been found that the methods and the luster lacquers used for this purpose can excellently be used for coloring quartz envelopes of halogen lamps.

The attractiveness of luster layers on porcelain and the like consists in addition to its natural colors of the shades which are formed in the luster layers by interference of the incident light. These light effects by interference play no part in the application on halogen lamps, but the ready resistance against a continuous temperature load as it occurs in halogen lamps, the ready adhesion to quartz, and the simple manner of application do. it has furthermore been found that in these layers the low coefficient of expansion of quartz has no disadvantageous results.

It is known that during operation of lamps having an envellglpe of quartz, devitrification may occur.

is devitrification is caused by traces of oil and perspiration which are introduced on the bulb manually upon touching. During operation, components thereof difi'use into the quartz and cause devitrification therein. Packing of the lamps should therefore be carried out with great accuracy and touching with the hands should be avoided as well as in mounting said lamps in lighting fittings.

It has been found that in spite of the presence of ethereal oils in luster lacquers, devitrification upon baking the lacquers does not occur while also afterwards during operation of the lamp no devitrification of the quartz occurs. It has also been found that the thin metal oxide layer which is obtained with the luster lacquer provides a sufficient protection against devitrification by perspiration and oil. This involves a saving of packaging material and labor since in this case packaging need not be carried out with so many precautions. Hence mounting of the lamps according to the invention also becomes simpler. Luster lacquers as such are commercially available.

As an example of a yellow luster lacquer may be mentioned a lacquer which contains two parts of bismuth resinate in three parts of uranium resinate, dissolved in a volatile oil, for examples camphor oil,-cedar oil or rosemary oil. The composition of the commercially available luster lacquers is usually unknown and hard to establish.

in order that the invention may be readily carried into effect, a few examples thereof will now be described in qreater detail.

EXAMPLE 1.

Manufacture of a yellow lamp The quartz envelope of a 6 volts, 55 watt lamp (car lamp) capacity approximately 0.25 ccm. which comprises a filament of tungsten and an atmosphere consisting of crypton to a pressure of 5 atmosphere and CH Br to a pressure of 7 mm. is coated, after the lamp was completed, with the aforesaid yellow luster lacquer by means of a brush.

After providing the lacquer layer it is dried in air for 30 minutes. The lacquer layer is then fired for l0 minutes in a fur.-

nace at a temperature between 550 and 700 C.

What is claimed is:

l. A halogen lamp comprising a quartz envelope, an external coating on said envelope, said coating comprising a layer of fired yellow-colored luster lacquer essentially consisting of two parts of bismuth resinate and three parts of uranium resinate dissolved in volatile oil.

2. A halogen lamp as claimed in claim 1 wherein said volatile oil comprises camphor oil.

3. A halogen lamp as claimed in claim 1 wherein said volatile oil comprises cedar oil.

4. A halogen lamp as claimed in claim 1 wherein said volatile oil comprises rosemary oil. 

2. A halogen lamp as claimed in claim 1 wherein said volatile oil comprises camphor oil.
 3. A halogen lamp as claimed in claim 1 wherein said volatile oil comprises cedar oil.
 4. A halogen lamp as claimed in claim 1 wherein said volatile oil comprises rosemary oil. 